The present invention relates to the feeding and tightening of threaded parts, such as bolts or nuts, and is intended to improve the nut runner or bolt runner which is in general use to provide an automatic version thereof. The invention in one embodiment incorporates a method of supplying the threaded parts to a predetermined objective position by operating a part-supply rod, provisionally storing them in a movable part-holding device before initiating transfer of said individual parts to this supply rod, and then causing the supply rod to properly supply each of these parts to the predetermined objective position. The present invention can incorporate a device for setting the axial position of a shaft-like part and a part-supply apparatus incorporating an axial-position setting device.
The present invention also relates to a detecting device for detecting the threaded parts while being held by the movable part-holding device of a parts feeding apparatus. More particularly, the detecting device is available for a part-supply system which supplies the threaded parts to a predetermined objective position by engaging each part with the part-holding device of a part-supply rod.
In the prior art, conventional parts-feeding devices comprise a rotary advance and retraction type feed rod having an engaging head with a mechanism for temporarily locking a threaded part fed onto the axis of the rod. The feed rod is advanced toward a part which is in the locked state, so that the engaging rod holds the part and feeds the latter to an intended place (i.e., to a mating part such as a threaded hole or a bolt) and concurrently effects tightening.
According to the prior art described above, a single mechanism has to perform both the positioning of a part on the axis of the feed rod and the temporary firm locking of the part. Therefore, such a mechanism must be necessarily of high precision, and even a slight decrease in precision would upset the correct engagement between the engaging head and the part, causing the problem of the part falling off. What should be given serious consideration is that such a locking mechanism makes it impossible to feed threaded parts to a narrow place. Further, the temporary locking of the part on the axis of the feed rod makes it necessary to limit the installation space for the temporary locking mechanism to a great extent or to install the mechanism in front of tile engaging head at a substantial distance from the latter. As a result, the apparatus is necessarily long in size. What is more important is that if the main body of a threaded part is hemispherical, with the conventional approach employed, that part cannot be held.
Typically, conventional part-supply systems initially cause each part to directly arrive at the axial line of a part-supply rod and then moves the part-supply rod forward in order that each part can properly be supplied to a predetermined objective position. Such a conventional arrangement has been disclosed, for example, in the Japanese Laid-Open Patent Publication No. 60131167 of 1985 according to a proposal of Yutani Iron Works, Ltd. Concretely, this system directly supplies each part onto the axial line of a part-supply rod so that the delivered part can be attracted on the surface of a magnet and then moves the part-supply rod forward in order to hold the delivered part before transferring it to a predetermined objective position.
According to the prior art cited above, those sequential steps are serially executed, which include a step of the individual part arriving at the axial line of the part supply rod and another step for the part-supply rod to hold the part before delivering it to a predetermined objective position. Consequently, the time needed for implementing both steps makes up a summative value. This in turn obstructs the need to promote operating efficiency.
Also in the prior art, the Japanese Laid-Open Patent Publication No. 60-131167 of 1985 (based on the art proposed by Yutani Iron Works, Ltd.) disclosed setting a specific position of a circular-sectional shaft-like part which causes a bolt substantially corresponding to a shaft-like part to be absorbed on the surface of a plane magnet so that the bolt can be set to a position coaxial with a part-supply rod provided for the proposed part-supply system.
However, since the supplied bolt is positioned merely by being absorbed on the surface of a magnet, the correct position of the supplied bolt cannot in any way be determined in any of the operating routines. Furthermore, even when operating an industrial robot system which frequently shifts its own posture and position and quickly halts itself, unless the supplied part is securely retained, the delivered part easily deviates its position as a result of inertial force. Thus, the delivered part cannot correctly be engaged with the part-supply rod.
As noted in the above discussion, there are a variety of conventional part-supply systems which provisionally engage individual parts to enable the following part-supply rod to hold the supplied part. However, no practical means has ever been provided for any of these conventional part-supply systems to check and confirm whether or not the supplied part is correctly held at the predetermined objective position, or whether the supplied part has already arrived at this predetermined position.
Therefore, conventional part-supply systems have a critical problem to overcome. For example, any conventional part-supply system cannot properly be operated when the supplied part is not properly engaged with a part-supply rod or not delivered to it due to a part's deviated position or its actual absence from the part-supply rod.